TABLE 1.

Sample types and testing for diagnosis of congenital and maternal CMV infection^a

Sample type	Method	Timing of evaluation	Sens/Spec	Comments	References
Diagnosis of maternal primary CMV infection
Serum	Serology: CMV IgG	<16 weeks’ gestation	97%–100%/96%–100%	Demonstration of seroconversion (IgG negative to positive) is definitive of primary infection	(10)
	CMV IgM		54%–100%/62%–100%	IgM should not be used alone for diagnosis of primary infection due to poor sensitivity and specificity	(10–17)
	CMV IgG avidity		85%/>90%	For IgM- and IgG-positive samples, avidity is needed to determine recent primary infection	(18, 19)
Diagnosis of congenital CMV in the fetus
Amniotic fluid	NAAT	6 weeks after maternal infection >21 weeks’ gestation	90%–95%/99%	Recommended sample type for diagnosis of fetal infection	(8, 20)
Chorionic villi, umbilical cord blood	NAAT	NA	ND	Alternate sample type for diagnosis of fetal infection Not recommended due to increased risk to fetus during sample collection	(21–23)
Diagnosis of congenital CMV in infant or older child
Urine	NAAT	<3 weeks old	98.8%–100.0%/99%	Most specific sample for diagnosis in neonatal period More difficult to collect than saliva Should be confirmed by testing a new sample (urine or saliva) collected for >3 weeks of life.	(24, 25)
Saliva	NAAT	<3 weeks old	97.4%–100.0%/91.5%–99.9%	Lacks specificity for diagnosis in the neonatal period due to contamination by breast milk Easy to obtain so used as screening sample Collect 1–2 h after breastfeeding Must be confirmed if positive by testing a new sample (urine or saliva) collected >3 weeks of life.	(26, 27)
Dried blood spotb	NAAT	>3 weeks old	34.4%–76.8%/99.9%	Used for retrospective diagnosis of congenital CMV Sensitivity lower than urine or saliva Negative result does not rule out congenital CMV	(28, 29)
Blood, viral load	NAAT	<3 weeks old	ND	Not recommended for screening for congenital CMV Low sensitivity: 10%–20% of congenitally infected CMV infants are positive If detected in blood, diagnostic for congenital CMV Has limited use to monitor therapy	(26, 30)
Serum	Serology CMV IgG CMV IgM	NA	ND	Not helpful in diagnosis of congenital CMV Maternal IgG detectable for up to 6–12 months Not useful due to lack of sensitivity and specificity	(31, 32)

^a NA, not available; NAAT, nucleic acid amplification testing; ND, not detected; Sens, sensitivity; Spec, specificity.

^b Sample collected at birth.